That's essentially how the UK does motorway junctions. Lanes go to different places, road signs a few miles in advance and written in white on the lanes. Generally we don't bother with the U turn options as relatively few people want to go in the opposite direction.<p>If it looks like magic, your country is doing this wrong.<p>Benefits of said junction include noone needing to slow down. Drawbacks include some fraction of people accidentally going in a direction they didn't want, using quite a lot of land, general construction cost.